POST-ADOLESCENT BRAIN MATURATION

It has been a long-held belief that the human brain stopped developing in adolescence. However, in 2011 two researchers from the Faculty of Medicine & Dentistry at the University of Alberta demonstrated that the human brain does not stop developing at adolescence, but instead continues well into the 20s. The study revealed that parts of the brain continue to develop post-adolescence within individual subjects.

Research shows that young adult brains are continuing to develop wiring to the frontal lobe; tracts responsible for complex cognitive tasks such as inhibition, high-level functioning, and attention. This may be due to a plethora of life experiences in young adulthood, such as pursing post-secondary education, starting a career, independence, and developing new social and family relationships. Unfortunately, because the research in this area of development is relatively new, the number of studies is limited.

Abstract: Maturation of the striatum has been posited to play a primary role in observed increases in adolescent sensation-seeking. However, evidence of neurophysiological maturation in the human adolescent striatum is limited. We applied T2*-weighted imaging, reflecting indices of tissue—iron concentration,to provide direct in vivo evidence of neurophysiological development of the human adolescent striatum. Multivariate pattern analysis (MVPA) of striatal T2*-weighted signal generated age predictions that accounted for over 60% of the sample variance in 10–25 year olds, using both task-related and resting state fMRI. Dorsal and ventral striatum showed age related increases and decreases respectively of striatal neurophysiology suggesting qualitative differences in the maturation of limbic and executive striatal systems. In particular, the ventral striatum was found to show the greatest developmental differences and contribute most heavily to the multivariate age predictor. The relationship of the T2*-weighted signal to the striatal dopamine system is discussed. Together, results provide evidence for protracted maturation of the striatum through adolescence. Read the full article.

“Longitudinal Development of Human Brain Wiring Continues from Childhood into Adulthood” by Catherine Lebel and Christian Beaulieu, The Journal of Neuroscience (2011)

Abstract:Read the full article Healthy human brain development is a complex process that continues during childhood and adolescence, as demonstrated by many cross-sectional and several longitudinal studies. However, whether these changes end in adolescence is not clear. We examined longitudinal white matter maturation using diffusion tensor tractography in 103 healthy subjects aged 5–32 years; each volunteer was scanned at least twice, with 221 total scans. Fractional anisotropy (FA) and mean diffusivity (MD), parameters indicative of factors including myelination and axon density, were assessed in 10 major white matter tracts. All tracts showed significant nonlinear development trajectories for FA and MD. Significant within-subject changes occurred in the vast majority of children and early adolescents, and these changes were mostly complete by late adolescence for projection and commissural tracts. However, association tracts demonstrated postadolescent within-subject maturation of both FA and MD. Diffusion parameter changes were due primarily to decreasing perpendicular diffusivity, although increasing parallel diffusivity contributed to the prolonged increases of FA in association tracts. Volume increased significantly with age for most tracts, and longitudinal measures also demonstrated postadolescent volume increases in several association tracts. As volume increases were not directly associated with either elevated FA or reduced MD between scans, the observed diffusion parameter changes likely reflect microstructural maturation of brain white matter tracts rather than just gross anatomy. Read the full article.

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